THE ADVANTAGES OF OVERHEAD CAMSHAFTS–WHAT ARE THEY?

This paper describes a detailed evaluation of overhead camshaft valve actuation. The conventional pushrod-operated valve train is compared to direct-acting and rocker-actuated overhead camshaft systems by both analytical and experimental means. The effect of the various methods of valve actuation on valve train weights, forces, and stresses is discussed. It is shown that the principal advantage of overhead camshafts is the increased natural frequency of the valve train. The resulting improved dynamic characteristics of the valve-actuating mechanism make it possible to design camshaft profiles which expand the useful operating range of high-speed engines.